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Deployment Guide

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12 Dell EMC Networking Virtualization Overlay with BGP EVPN
4 Topology
4.1 Leaf-spine underlay
This deployment uses a Layer 3 leaf-spine topology for the network underlay. The underlay provides transit
for the virtual network overlays.
In a Layer 3 leaf-spine network, traffic between leafs and spines is routed. Equal cost multi-path routing
(ECMP) is used to load balance traffic across the Layer 3 connections. BGP is used to exchange routes. The
Layer 3/Layer 2 (L3/L2) boundary is at the leaf switches.
Two leaf switches are configured as Virtual Link Trunking (VLT) peers at the top of each rack. VLT allows all
connections to be active while also providing fault tolerance. As administrators add racks to the data center,
two leaf switches configured for VLT are added to each new rack. Connections within racks from hosts to leaf
switches are Layer 2, and each host is connected using a VLT port channel.
In this example, two Z9264F-ON switches are used as spines, two S5248F-ON switches are used as leafs in
Rack 1, and four S4148U-ON switches are used as leafs in the remaining two racks. The leafs in the last rack
also act as border leafs.
Note: For this deployment example, any leaf pair may be used as border leafs, and hosts may also be
connected to the border leafs.
For demonstration purposes, there is an additional switch attached to the border leafs which serves as a
simulated gateway/firewall for connections to the external network as shown in Figure 8.
Leaf-spine underlay network
Note: Using a leaf-spine network in the data center is considered a best practice. With Z9264F-ON switches
as spines and two leaf switches per rack, this topology will scale to 32 racks. For additional leaf-spine network
information, refer to Dell EMC PowerSwitch Layer 3 Leaf-Spine Deployment and Best Practices with OS10.
There are some BGP configuration differences in this guide to enable the BGP EVPN VXLAN feature.